The Triple Crown finale is the series’ oldest, dating to 1867, and covers the most ground. That never changes. But what is the historical significance of the Belmont Stakes? Well, that depends upon the circumstances.

A year ago, the long lap around Big Sandy truly was “The Test of the Champion,” as American Pharoah raced into immortality with the first sweep of the 3-year-old classics since Affirmed in 1978. Those 2½ minutes at Belmont Park culminated in the ultimate feel-good moment for racing, a deliverance from almost four decades of frustration.

Yet in other years, the 1½-mile marathon is “The Triumph of the One-Hit Wonder.” Remember the impossible long shots Da’ Tara, in 2008, and Ruler on Ice, in 2011, who had a brief shining moment and disappeared. Da’ Tara lost his next 11 races and finished his career 2-for-19. Ruler on Ice did a 1-for-16 encore and ended up 4-for-23.

Conversely, so many great horses lost in the Belmont. Among them is Curlin, the Horse of the Year in 2007 and 2008 and the sire of Saturday’s favorite, Preakness hero Exaggerator. Curlin stands at stud in Lexington, Kentucky, at Hill ‘n’ Dale Farm, which bought a 20-percent interest in him last summer from Barbara Banke, who moved the horse from nearby Lane’s End Farm. Hill ‘n’ Dale’s investment paid off almost immediately, because within weeks Curlin’s son Keen Ice upset American Pharoah in the Travers at Saratoga. During the winter, Curlin’s daughter Stellar Wind was voted champion 3-year-old filly.

Hill ‘n’ Dale’s president, John Sikura, is rooting for Exaggerator because a win would reflect positively on his sire, who stands for $100,000 per mating. Yet to breeders, the Belmont is the least important classic, unless it completes a sweep. Pharoah would not be commanding $200,000 per breeding session at Ashford Stud if he’d come up short in Elmont.

“To the general public, the Kentucky Derby is the defining race for the thoroughbred,’’ Sikura told Newsday. “If you could pick a classic to win for your bucket list, it would be the Derby, but a Preakness win would be a great consolation prize.

“The Belmont has a little less cachet because it’s a mile and a half. Some of the horses who won it didn’t do much before or after, because sometimes a horse wins just because he stays the distance better than the rest of them, not because he’s a better horse.”

American breeders shifted the emphasis from stamina to speed during the 1980s. In that spendthrift decade, yearling prices climbed into the millions, and six-figure stakes for 2-year-olds sprouted like mushrooms. When an owner lays out megabucks for a fashionably bred young thoroughbred, a quick return on investment is the best reward.

The Belmont is America’s only high-profile dirt race at 12 furlongs. So unless a horse excels at shorter distances, too, a Belmont victory means a lot less. Exaggerator has won from 5 furlongs to 1 3/16 miles, so he’s a very attractive stallion prospect, and two months ago WinStar Farm invested heavily in his genes. If Exaggerator wins Saturday, he’ll be the first Derby runner-up in 61 years to hit the Preakness-Belmont double. Sikura thinks that would be “the cherry on top” and could have a ripple effect on the quality of the mares Curlin attracts.

“Exaggerator is a very good horse, and I hope he does well in the Belmont,’’ Sikura said. “To compete successfully in all three races, you’ve had a heck of a run. We’re all-in on Curlin, and it would be a little more evidence to swing the verdict our way.

“It’s been a nice story for us. Last year was a good year to buy into Curlin. I thought he was poised to be a world-class sire, and he changed from a horse with potential to a horse who arrived.

“We hope the story continues next year.”